COIN-OR::LEMON - Graph Library

source: lemon-1.2/lemon/bfs.h @ 387:24a2c6ee6cb0

Last change on this file since 387:24a2c6ee6cb0 was 329:d900fd1e760f, checked in by Peter Kovacs <kpeter@…>, 11 years ago

Print the failed line numbers in the unifier script (ticket #138)

File size: 54.2 KB
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1/* -*- mode: C++; indent-tabs-mode: nil; -*-
2 *
3 * This file is a part of LEMON, a generic C++ optimization library.
4 *
5 * Copyright (C) 2003-2008
6 * Egervary Jeno Kombinatorikus Optimalizalasi Kutatocsoport
7 * (Egervary Research Group on Combinatorial Optimization, EGRES).
8 *
9 * Permission to use, modify and distribute this software is granted
10 * provided that this copyright notice appears in all copies. For
11 * precise terms see the accompanying LICENSE file.
12 *
13 * This software is provided "AS IS" with no warranty of any kind,
14 * express or implied, and with no claim as to its suitability for any
15 * purpose.
16 *
17 */
18
19#ifndef LEMON_BFS_H
20#define LEMON_BFS_H
21
22///\ingroup search
23///\file
24///\brief BFS algorithm.
25
26#include <lemon/list_graph.h>
27#include <lemon/bits/path_dump.h>
28#include <lemon/core.h>
29#include <lemon/error.h>
30#include <lemon/maps.h>
31#include <lemon/path.h>
32
33namespace lemon {
34
35  ///Default traits class of Bfs class.
36
37  ///Default traits class of Bfs class.
38  ///\tparam GR Digraph type.
39  template<class GR>
40  struct BfsDefaultTraits
41  {
42    ///The type of the digraph the algorithm runs on.
43    typedef GR Digraph;
44
45    ///\brief The type of the map that stores the predecessor
46    ///arcs of the shortest paths.
47    ///
48    ///The type of the map that stores the predecessor
49    ///arcs of the shortest paths.
50    ///It must meet the \ref concepts::WriteMap "WriteMap" concept.
51    typedef typename Digraph::template NodeMap<typename Digraph::Arc> PredMap;
52    ///Instantiates a PredMap.
53
54    ///This function instantiates a PredMap. 
55    ///\param g is the digraph, to which we would like to define the
56    ///PredMap.
57    static PredMap *createPredMap(const Digraph &g)
58    {
59      return new PredMap(g);
60    }
61
62    ///The type of the map that indicates which nodes are processed.
63
64    ///The type of the map that indicates which nodes are processed.
65    ///It must meet the \ref concepts::WriteMap "WriteMap" concept.
66    typedef NullMap<typename Digraph::Node,bool> ProcessedMap;
67    ///Instantiates a ProcessedMap.
68
69    ///This function instantiates a ProcessedMap.
70    ///\param g is the digraph, to which
71    ///we would like to define the ProcessedMap
72#ifdef DOXYGEN
73    static ProcessedMap *createProcessedMap(const Digraph &g)
74#else
75    static ProcessedMap *createProcessedMap(const Digraph &)
76#endif
77    {
78      return new ProcessedMap();
79    }
80
81    ///The type of the map that indicates which nodes are reached.
82
83    ///The type of the map that indicates which nodes are reached.///It must meet the \ref concepts::ReadWriteMap "ReadWriteMap" concept.
84    typedef typename Digraph::template NodeMap<bool> ReachedMap;
85    ///Instantiates a ReachedMap.
86
87    ///This function instantiates a ReachedMap.
88    ///\param g is the digraph, to which
89    ///we would like to define the ReachedMap.
90    static ReachedMap *createReachedMap(const Digraph &g)
91    {
92      return new ReachedMap(g);
93    }
94
95    ///The type of the map that stores the distances of the nodes.
96
97    ///The type of the map that stores the distances of the nodes.
98    ///It must meet the \ref concepts::WriteMap "WriteMap" concept.
99    typedef typename Digraph::template NodeMap<int> DistMap;
100    ///Instantiates a DistMap.
101
102    ///This function instantiates a DistMap.
103    ///\param g is the digraph, to which we would like to define the
104    ///DistMap.
105    static DistMap *createDistMap(const Digraph &g)
106    {
107      return new DistMap(g);
108    }
109  };
110
111  ///%BFS algorithm class.
112
113  ///\ingroup search
114  ///This class provides an efficient implementation of the %BFS algorithm.
115  ///
116  ///There is also a \ref bfs() "function-type interface" for the BFS
117  ///algorithm, which is convenient in the simplier cases and it can be
118  ///used easier.
119  ///
120  ///\tparam GR The type of the digraph the algorithm runs on.
121  ///The default value is \ref ListDigraph. The value of GR is not used
122  ///directly by \ref Bfs, it is only passed to \ref BfsDefaultTraits.
123  ///\tparam TR Traits class to set various data types used by the algorithm.
124  ///The default traits class is
125  ///\ref BfsDefaultTraits "BfsDefaultTraits<GR>".
126  ///See \ref BfsDefaultTraits for the documentation of
127  ///a Bfs traits class.
128#ifdef DOXYGEN
129  template <typename GR,
130            typename TR>
131#else
132  template <typename GR=ListDigraph,
133            typename TR=BfsDefaultTraits<GR> >
134#endif
135  class Bfs {
136  public:
137
138    ///The type of the digraph the algorithm runs on.
139    typedef typename TR::Digraph Digraph;
140
141    ///\brief The type of the map that stores the predecessor arcs of the
142    ///shortest paths.
143    typedef typename TR::PredMap PredMap;
144    ///The type of the map that stores the distances of the nodes.
145    typedef typename TR::DistMap DistMap;
146    ///The type of the map that indicates which nodes are reached.
147    typedef typename TR::ReachedMap ReachedMap;
148    ///The type of the map that indicates which nodes are processed.
149    typedef typename TR::ProcessedMap ProcessedMap;
150    ///The type of the paths.
151    typedef PredMapPath<Digraph, PredMap> Path;
152
153    ///The traits class.
154    typedef TR Traits;
155
156  private:
157
158    typedef typename Digraph::Node Node;
159    typedef typename Digraph::NodeIt NodeIt;
160    typedef typename Digraph::Arc Arc;
161    typedef typename Digraph::OutArcIt OutArcIt;
162
163    //Pointer to the underlying digraph.
164    const Digraph *G;
165    //Pointer to the map of predecessor arcs.
166    PredMap *_pred;
167    //Indicates if _pred is locally allocated (true) or not.
168    bool local_pred;
169    //Pointer to the map of distances.
170    DistMap *_dist;
171    //Indicates if _dist is locally allocated (true) or not.
172    bool local_dist;
173    //Pointer to the map of reached status of the nodes.
174    ReachedMap *_reached;
175    //Indicates if _reached is locally allocated (true) or not.
176    bool local_reached;
177    //Pointer to the map of processed status of the nodes.
178    ProcessedMap *_processed;
179    //Indicates if _processed is locally allocated (true) or not.
180    bool local_processed;
181
182    std::vector<typename Digraph::Node> _queue;
183    int _queue_head,_queue_tail,_queue_next_dist;
184    int _curr_dist;
185
186    //Creates the maps if necessary.
187    void create_maps()
188    {
189      if(!_pred) {
190        local_pred = true;
191        _pred = Traits::createPredMap(*G);
192      }
193      if(!_dist) {
194        local_dist = true;
195        _dist = Traits::createDistMap(*G);
196      }
197      if(!_reached) {
198        local_reached = true;
199        _reached = Traits::createReachedMap(*G);
200      }
201      if(!_processed) {
202        local_processed = true;
203        _processed = Traits::createProcessedMap(*G);
204      }
205    }
206
207  protected:
208
209    Bfs() {}
210
211  public:
212
213    typedef Bfs Create;
214
215    ///\name Named template parameters
216
217    ///@{
218
219    template <class T>
220    struct SetPredMapTraits : public Traits {
221      typedef T PredMap;
222      static PredMap *createPredMap(const Digraph &)
223      {
224        LEMON_ASSERT(false, "PredMap is not initialized");
225        return 0; // ignore warnings
226      }
227    };
228    ///\brief \ref named-templ-param "Named parameter" for setting
229    ///PredMap type.
230    ///
231    ///\ref named-templ-param "Named parameter" for setting
232    ///PredMap type.
233    template <class T>
234    struct SetPredMap : public Bfs< Digraph, SetPredMapTraits<T> > {
235      typedef Bfs< Digraph, SetPredMapTraits<T> > Create;
236    };
237
238    template <class T>
239    struct SetDistMapTraits : public Traits {
240      typedef T DistMap;
241      static DistMap *createDistMap(const Digraph &)
242      {
243        LEMON_ASSERT(false, "DistMap is not initialized");
244        return 0; // ignore warnings
245      }
246    };
247    ///\brief \ref named-templ-param "Named parameter" for setting
248    ///DistMap type.
249    ///
250    ///\ref named-templ-param "Named parameter" for setting
251    ///DistMap type.
252    template <class T>
253    struct SetDistMap : public Bfs< Digraph, SetDistMapTraits<T> > {
254      typedef Bfs< Digraph, SetDistMapTraits<T> > Create;
255    };
256
257    template <class T>
258    struct SetReachedMapTraits : public Traits {
259      typedef T ReachedMap;
260      static ReachedMap *createReachedMap(const Digraph &)
261      {
262        LEMON_ASSERT(false, "ReachedMap is not initialized");
263        return 0; // ignore warnings
264      }
265    };
266    ///\brief \ref named-templ-param "Named parameter" for setting
267    ///ReachedMap type.
268    ///
269    ///\ref named-templ-param "Named parameter" for setting
270    ///ReachedMap type.
271    template <class T>
272    struct SetReachedMap : public Bfs< Digraph, SetReachedMapTraits<T> > {
273      typedef Bfs< Digraph, SetReachedMapTraits<T> > Create;
274    };
275
276    template <class T>
277    struct SetProcessedMapTraits : public Traits {
278      typedef T ProcessedMap;
279      static ProcessedMap *createProcessedMap(const Digraph &)
280      {
281        LEMON_ASSERT(false, "ProcessedMap is not initialized");
282        return 0; // ignore warnings
283      }
284    };
285    ///\brief \ref named-templ-param "Named parameter" for setting
286    ///ProcessedMap type.
287    ///
288    ///\ref named-templ-param "Named parameter" for setting
289    ///ProcessedMap type.
290    template <class T>
291    struct SetProcessedMap : public Bfs< Digraph, SetProcessedMapTraits<T> > {
292      typedef Bfs< Digraph, SetProcessedMapTraits<T> > Create;
293    };
294
295    struct SetStandardProcessedMapTraits : public Traits {
296      typedef typename Digraph::template NodeMap<bool> ProcessedMap;
297      static ProcessedMap *createProcessedMap(const Digraph &g)
298      {
299        return new ProcessedMap(g);
300        return 0; // ignore warnings
301      }
302    };
303    ///\brief \ref named-templ-param "Named parameter" for setting
304    ///ProcessedMap type to be <tt>Digraph::NodeMap<bool></tt>.
305    ///
306    ///\ref named-templ-param "Named parameter" for setting
307    ///ProcessedMap type to be <tt>Digraph::NodeMap<bool></tt>.
308    ///If you don't set it explicitly, it will be automatically allocated.
309    struct SetStandardProcessedMap :
310      public Bfs< Digraph, SetStandardProcessedMapTraits > {
311      typedef Bfs< Digraph, SetStandardProcessedMapTraits > Create;
312    };
313
314    ///@}
315
316  public:
317
318    ///Constructor.
319
320    ///Constructor.
321    ///\param g The digraph the algorithm runs on.
322    Bfs(const Digraph &g) :
323      G(&g),
324      _pred(NULL), local_pred(false),
325      _dist(NULL), local_dist(false),
326      _reached(NULL), local_reached(false),
327      _processed(NULL), local_processed(false)
328    { }
329
330    ///Destructor.
331    ~Bfs()
332    {
333      if(local_pred) delete _pred;
334      if(local_dist) delete _dist;
335      if(local_reached) delete _reached;
336      if(local_processed) delete _processed;
337    }
338
339    ///Sets the map that stores the predecessor arcs.
340
341    ///Sets the map that stores the predecessor arcs.
342    ///If you don't use this function before calling \ref run(),
343    ///it will allocate one. The destructor deallocates this
344    ///automatically allocated map, of course.
345    ///\return <tt> (*this) </tt>
346    Bfs &predMap(PredMap &m)
347    {
348      if(local_pred) {
349        delete _pred;
350        local_pred=false;
351      }
352      _pred = &m;
353      return *this;
354    }
355
356    ///Sets the map that indicates which nodes are reached.
357
358    ///Sets the map that indicates which nodes are reached.
359    ///If you don't use this function before calling \ref run(),
360    ///it will allocate one. The destructor deallocates this
361    ///automatically allocated map, of course.
362    ///\return <tt> (*this) </tt>
363    Bfs &reachedMap(ReachedMap &m)
364    {
365      if(local_reached) {
366        delete _reached;
367        local_reached=false;
368      }
369      _reached = &m;
370      return *this;
371    }
372
373    ///Sets the map that indicates which nodes are processed.
374
375    ///Sets the map that indicates which nodes are processed.
376    ///If you don't use this function before calling \ref run(),
377    ///it will allocate one. The destructor deallocates this
378    ///automatically allocated map, of course.
379    ///\return <tt> (*this) </tt>
380    Bfs &processedMap(ProcessedMap &m)
381    {
382      if(local_processed) {
383        delete _processed;
384        local_processed=false;
385      }
386      _processed = &m;
387      return *this;
388    }
389
390    ///Sets the map that stores the distances of the nodes.
391
392    ///Sets the map that stores the distances of the nodes calculated by
393    ///the algorithm.
394    ///If you don't use this function before calling \ref run(),
395    ///it will allocate one. The destructor deallocates this
396    ///automatically allocated map, of course.
397    ///\return <tt> (*this) </tt>
398    Bfs &distMap(DistMap &m)
399    {
400      if(local_dist) {
401        delete _dist;
402        local_dist=false;
403      }
404      _dist = &m;
405      return *this;
406    }
407
408  public:
409
410    ///\name Execution control
411    ///The simplest way to execute the algorithm is to use
412    ///one of the member functions called \ref lemon::Bfs::run() "run()".
413    ///\n
414    ///If you need more control on the execution, first you must call
415    ///\ref lemon::Bfs::init() "init()", then you can add several source
416    ///nodes with \ref lemon::Bfs::addSource() "addSource()".
417    ///Finally \ref lemon::Bfs::start() "start()" will perform the
418    ///actual path computation.
419
420    ///@{
421
422    ///Initializes the internal data structures.
423
424    ///Initializes the internal data structures.
425    ///
426    void init()
427    {
428      create_maps();
429      _queue.resize(countNodes(*G));
430      _queue_head=_queue_tail=0;
431      _curr_dist=1;
432      for ( NodeIt u(*G) ; u!=INVALID ; ++u ) {
433        _pred->set(u,INVALID);
434        _reached->set(u,false);
435        _processed->set(u,false);
436      }
437    }
438
439    ///Adds a new source node.
440
441    ///Adds a new source node to the set of nodes to be processed.
442    ///
443    void addSource(Node s)
444    {
445      if(!(*_reached)[s])
446        {
447          _reached->set(s,true);
448          _pred->set(s,INVALID);
449          _dist->set(s,0);
450          _queue[_queue_head++]=s;
451          _queue_next_dist=_queue_head;
452        }
453    }
454
455    ///Processes the next node.
456
457    ///Processes the next node.
458    ///
459    ///\return The processed node.
460    ///
461    ///\pre The queue must not be empty.
462    Node processNextNode()
463    {
464      if(_queue_tail==_queue_next_dist) {
465        _curr_dist++;
466        _queue_next_dist=_queue_head;
467      }
468      Node n=_queue[_queue_tail++];
469      _processed->set(n,true);
470      Node m;
471      for(OutArcIt e(*G,n);e!=INVALID;++e)
472        if(!(*_reached)[m=G->target(e)]) {
473          _queue[_queue_head++]=m;
474          _reached->set(m,true);
475          _pred->set(m,e);
476          _dist->set(m,_curr_dist);
477        }
478      return n;
479    }
480
481    ///Processes the next node.
482
483    ///Processes the next node and checks if the given target node
484    ///is reached. If the target node is reachable from the processed
485    ///node, then the \c reach parameter will be set to \c true.
486    ///
487    ///\param target The target node.
488    ///\retval reach Indicates if the target node is reached.
489    ///It should be initially \c false.
490    ///
491    ///\return The processed node.
492    ///
493    ///\pre The queue must not be empty.
494    Node processNextNode(Node target, bool& reach)
495    {
496      if(_queue_tail==_queue_next_dist) {
497        _curr_dist++;
498        _queue_next_dist=_queue_head;
499      }
500      Node n=_queue[_queue_tail++];
501      _processed->set(n,true);
502      Node m;
503      for(OutArcIt e(*G,n);e!=INVALID;++e)
504        if(!(*_reached)[m=G->target(e)]) {
505          _queue[_queue_head++]=m;
506          _reached->set(m,true);
507          _pred->set(m,e);
508          _dist->set(m,_curr_dist);
509          reach = reach || (target == m);
510        }
511      return n;
512    }
513
514    ///Processes the next node.
515
516    ///Processes the next node and checks if at least one of reached
517    ///nodes has \c true value in the \c nm node map. If one node
518    ///with \c true value is reachable from the processed node, then the
519    ///\c rnode parameter will be set to the first of such nodes.
520    ///
521    ///\param nm A \c bool (or convertible) node map that indicates the
522    ///possible targets.
523    ///\retval rnode The reached target node.
524    ///It should be initially \c INVALID.
525    ///
526    ///\return The processed node.
527    ///
528    ///\pre The queue must not be empty.
529    template<class NM>
530    Node processNextNode(const NM& nm, Node& rnode)
531    {
532      if(_queue_tail==_queue_next_dist) {
533        _curr_dist++;
534        _queue_next_dist=_queue_head;
535      }
536      Node n=_queue[_queue_tail++];
537      _processed->set(n,true);
538      Node m;
539      for(OutArcIt e(*G,n);e!=INVALID;++e)
540        if(!(*_reached)[m=G->target(e)]) {
541          _queue[_queue_head++]=m;
542          _reached->set(m,true);
543          _pred->set(m,e);
544          _dist->set(m,_curr_dist);
545          if (nm[m] && rnode == INVALID) rnode = m;
546        }
547      return n;
548    }
549
550    ///The next node to be processed.
551
552    ///Returns the next node to be processed or \c INVALID if the queue
553    ///is empty.
554    Node nextNode() const
555    {
556      return _queue_tail<_queue_head?_queue[_queue_tail]:INVALID;
557    }
558
559    ///\brief Returns \c false if there are nodes
560    ///to be processed.
561    ///
562    ///Returns \c false if there are nodes
563    ///to be processed in the queue.
564    bool emptyQueue() const { return _queue_tail==_queue_head; }
565
566    ///Returns the number of the nodes to be processed.
567
568    ///Returns the number of the nodes to be processed in the queue.
569    int queueSize() const { return _queue_head-_queue_tail; }
570
571    ///Executes the algorithm.
572
573    ///Executes the algorithm.
574    ///
575    ///This method runs the %BFS algorithm from the root node(s)
576    ///in order to compute the shortest path to each node.
577    ///
578    ///The algorithm computes
579    ///- the shortest path tree (forest),
580    ///- the distance of each node from the root(s).
581    ///
582    ///\pre init() must be called and at least one root node should be
583    ///added with addSource() before using this function.
584    ///
585    ///\note <tt>b.start()</tt> is just a shortcut of the following code.
586    ///\code
587    ///  while ( !b.emptyQueue() ) {
588    ///    b.processNextNode();
589    ///  }
590    ///\endcode
591    void start()
592    {
593      while ( !emptyQueue() ) processNextNode();
594    }
595
596    ///Executes the algorithm until the given target node is reached.
597
598    ///Executes the algorithm until the given target node is reached.
599    ///
600    ///This method runs the %BFS algorithm from the root node(s)
601    ///in order to compute the shortest path to \c t.
602    ///
603    ///The algorithm computes
604    ///- the shortest path to \c t,
605    ///- the distance of \c t from the root(s).
606    ///
607    ///\pre init() must be called and at least one root node should be
608    ///added with addSource() before using this function.
609    ///
610    ///\note <tt>b.start(t)</tt> is just a shortcut of the following code.
611    ///\code
612    ///  bool reach = false;
613    ///  while ( !b.emptyQueue() && !reach ) {
614    ///    b.processNextNode(t, reach);
615    ///  }
616    ///\endcode
617    void start(Node t)
618    {
619      bool reach = false;
620      while ( !emptyQueue() && !reach ) processNextNode(t, reach);
621    }
622
623    ///Executes the algorithm until a condition is met.
624
625    ///Executes the algorithm until a condition is met.
626    ///
627    ///This method runs the %BFS algorithm from the root node(s) in
628    ///order to compute the shortest path to a node \c v with
629    /// <tt>nm[v]</tt> true, if such a node can be found.
630    ///
631    ///\param nm A \c bool (or convertible) node map. The algorithm
632    ///will stop when it reaches a node \c v with <tt>nm[v]</tt> true.
633    ///
634    ///\return The reached node \c v with <tt>nm[v]</tt> true or
635    ///\c INVALID if no such node was found.
636    ///
637    ///\pre init() must be called and at least one root node should be
638    ///added with addSource() before using this function.
639    ///
640    ///\note <tt>b.start(nm)</tt> is just a shortcut of the following code.
641    ///\code
642    ///  Node rnode = INVALID;
643    ///  while ( !b.emptyQueue() && rnode == INVALID ) {
644    ///    b.processNextNode(nm, rnode);
645    ///  }
646    ///  return rnode;
647    ///\endcode
648    template<class NodeBoolMap>
649    Node start(const NodeBoolMap &nm)
650    {
651      Node rnode = INVALID;
652      while ( !emptyQueue() && rnode == INVALID ) {
653        processNextNode(nm, rnode);
654      }
655      return rnode;
656    }
657
658    ///Runs the algorithm from the given source node.
659
660    ///This method runs the %BFS algorithm from node \c s
661    ///in order to compute the shortest path to each node.
662    ///
663    ///The algorithm computes
664    ///- the shortest path tree,
665    ///- the distance of each node from the root.
666    ///
667    ///\note <tt>b.run(s)</tt> is just a shortcut of the following code.
668    ///\code
669    ///  b.init();
670    ///  b.addSource(s);
671    ///  b.start();
672    ///\endcode
673    void run(Node s) {
674      init();
675      addSource(s);
676      start();
677    }
678
679    ///Finds the shortest path between \c s and \c t.
680
681    ///This method runs the %BFS algorithm from node \c s
682    ///in order to compute the shortest path to node \c t
683    ///(it stops searching when \c t is processed).
684    ///
685    ///\return \c true if \c t is reachable form \c s.
686    ///
687    ///\note Apart from the return value, <tt>b.run(s,t)</tt> is just a
688    ///shortcut of the following code.
689    ///\code
690    ///  b.init();
691    ///  b.addSource(s);
692    ///  b.start(t);
693    ///\endcode
694    bool run(Node s,Node t) {
695      init();
696      addSource(s);
697      start(t);
698      return reached(t);
699    }
700
701    ///Runs the algorithm to visit all nodes in the digraph.
702
703    ///This method runs the %BFS algorithm in order to
704    ///compute the shortest path to each node.
705    ///
706    ///The algorithm computes
707    ///- the shortest path tree (forest),
708    ///- the distance of each node from the root(s).
709    ///
710    ///\note <tt>b.run(s)</tt> is just a shortcut of the following code.
711    ///\code
712    ///  b.init();
713    ///  for (NodeIt n(gr); n != INVALID; ++n) {
714    ///    if (!b.reached(n)) {
715    ///      b.addSource(n);
716    ///      b.start();
717    ///    }
718    ///  }
719    ///\endcode
720    void run() {
721      init();
722      for (NodeIt n(*G); n != INVALID; ++n) {
723        if (!reached(n)) {
724          addSource(n);
725          start();
726        }
727      }
728    }
729
730    ///@}
731
732    ///\name Query Functions
733    ///The result of the %BFS algorithm can be obtained using these
734    ///functions.\n
735    ///Either \ref lemon::Bfs::run() "run()" or \ref lemon::Bfs::start()
736    ///"start()" must be called before using them.
737
738    ///@{
739
740    ///The shortest path to a node.
741
742    ///Returns the shortest path to a node.
743    ///
744    ///\warning \c t should be reachable from the root(s).
745    ///
746    ///\pre Either \ref run() or \ref start() must be called before
747    ///using this function.
748    Path path(Node t) const { return Path(*G, *_pred, t); }
749
750    ///The distance of a node from the root(s).
751
752    ///Returns the distance of a node from the root(s).
753    ///
754    ///\warning If node \c v is not reachable from the root(s), then
755    ///the return value of this function is undefined.
756    ///
757    ///\pre Either \ref run() or \ref start() must be called before
758    ///using this function.
759    int dist(Node v) const { return (*_dist)[v]; }
760
761    ///Returns the 'previous arc' of the shortest path tree for a node.
762
763    ///This function returns the 'previous arc' of the shortest path
764    ///tree for the node \c v, i.e. it returns the last arc of a
765    ///shortest path from the root(s) to \c v. It is \c INVALID if \c v
766    ///is not reachable from the root(s) or if \c v is a root.
767    ///
768    ///The shortest path tree used here is equal to the shortest path
769    ///tree used in \ref predNode().
770    ///
771    ///\pre Either \ref run() or \ref start() must be called before
772    ///using this function.
773    Arc predArc(Node v) const { return (*_pred)[v];}
774
775    ///Returns the 'previous node' of the shortest path tree for a node.
776
777    ///This function returns the 'previous node' of the shortest path
778    ///tree for the node \c v, i.e. it returns the last but one node
779    ///from a shortest path from the root(s) to \c v. It is \c INVALID
780    ///if \c v is not reachable from the root(s) or if \c v is a root.
781    ///
782    ///The shortest path tree used here is equal to the shortest path
783    ///tree used in \ref predArc().
784    ///
785    ///\pre Either \ref run() or \ref start() must be called before
786    ///using this function.
787    Node predNode(Node v) const { return (*_pred)[v]==INVALID ? INVALID:
788                                  G->source((*_pred)[v]); }
789
790    ///\brief Returns a const reference to the node map that stores the
791    /// distances of the nodes.
792    ///
793    ///Returns a const reference to the node map that stores the distances
794    ///of the nodes calculated by the algorithm.
795    ///
796    ///\pre Either \ref run() or \ref init()
797    ///must be called before using this function.
798    const DistMap &distMap() const { return *_dist;}
799
800    ///\brief Returns a const reference to the node map that stores the
801    ///predecessor arcs.
802    ///
803    ///Returns a const reference to the node map that stores the predecessor
804    ///arcs, which form the shortest path tree.
805    ///
806    ///\pre Either \ref run() or \ref init()
807    ///must be called before using this function.
808    const PredMap &predMap() const { return *_pred;}
809
810    ///Checks if a node is reachable from the root(s).
811
812    ///Returns \c true if \c v is reachable from the root(s).
813    ///\pre Either \ref run() or \ref start()
814    ///must be called before using this function.
815    bool reached(Node v) const { return (*_reached)[v]; }
816
817    ///@}
818  };
819
820  ///Default traits class of bfs() function.
821
822  ///Default traits class of bfs() function.
823  ///\tparam GR Digraph type.
824  template<class GR>
825  struct BfsWizardDefaultTraits
826  {
827    ///The type of the digraph the algorithm runs on.
828    typedef GR Digraph;
829
830    ///\brief The type of the map that stores the predecessor
831    ///arcs of the shortest paths.
832    ///
833    ///The type of the map that stores the predecessor
834    ///arcs of the shortest paths.
835    ///It must meet the \ref concepts::WriteMap "WriteMap" concept.
836    typedef typename Digraph::template NodeMap<typename Digraph::Arc> PredMap;
837    ///Instantiates a PredMap.
838
839    ///This function instantiates a PredMap.
840    ///\param g is the digraph, to which we would like to define the
841    ///PredMap.
842    static PredMap *createPredMap(const Digraph &g)
843    {
844      return new PredMap(g);
845    }
846
847    ///The type of the map that indicates which nodes are processed.
848
849    ///The type of the map that indicates which nodes are processed.
850    ///It must meet the \ref concepts::WriteMap "WriteMap" concept.
851    ///By default it is a NullMap.
852    typedef NullMap<typename Digraph::Node,bool> ProcessedMap;
853    ///Instantiates a ProcessedMap.
854
855    ///This function instantiates a ProcessedMap.
856    ///\param g is the digraph, to which
857    ///we would like to define the ProcessedMap.
858#ifdef DOXYGEN
859    static ProcessedMap *createProcessedMap(const Digraph &g)
860#else
861    static ProcessedMap *createProcessedMap(const Digraph &)
862#endif
863    {
864      return new ProcessedMap();
865    }
866
867    ///The type of the map that indicates which nodes are reached.
868
869    ///The type of the map that indicates which nodes are reached.
870    ///It must meet the \ref concepts::ReadWriteMap "ReadWriteMap" concept.
871    typedef typename Digraph::template NodeMap<bool> ReachedMap;
872    ///Instantiates a ReachedMap.
873
874    ///This function instantiates a ReachedMap.
875    ///\param g is the digraph, to which
876    ///we would like to define the ReachedMap.
877    static ReachedMap *createReachedMap(const Digraph &g)
878    {
879      return new ReachedMap(g);
880    }
881
882    ///The type of the map that stores the distances of the nodes.
883
884    ///The type of the map that stores the distances of the nodes.
885    ///It must meet the \ref concepts::WriteMap "WriteMap" concept.
886    typedef typename Digraph::template NodeMap<int> DistMap;
887    ///Instantiates a DistMap.
888
889    ///This function instantiates a DistMap.
890    ///\param g is the digraph, to which we would like to define
891    ///the DistMap
892    static DistMap *createDistMap(const Digraph &g)
893    {
894      return new DistMap(g);
895    }
896
897    ///The type of the shortest paths.
898
899    ///The type of the shortest paths.
900    ///It must meet the \ref concepts::Path "Path" concept.
901    typedef lemon::Path<Digraph> Path;
902  };
903
904  /// Default traits class used by BfsWizard
905
906  /// To make it easier to use Bfs algorithm
907  /// we have created a wizard class.
908  /// This \ref BfsWizard class needs default traits,
909  /// as well as the \ref Bfs class.
910  /// The \ref BfsWizardBase is a class to be the default traits of the
911  /// \ref BfsWizard class.
912  template<class GR>
913  class BfsWizardBase : public BfsWizardDefaultTraits<GR>
914  {
915
916    typedef BfsWizardDefaultTraits<GR> Base;
917  protected:
918    //The type of the nodes in the digraph.
919    typedef typename Base::Digraph::Node Node;
920
921    //Pointer to the digraph the algorithm runs on.
922    void *_g;
923    //Pointer to the map of reached nodes.
924    void *_reached;
925    //Pointer to the map of processed nodes.
926    void *_processed;
927    //Pointer to the map of predecessors arcs.
928    void *_pred;
929    //Pointer to the map of distances.
930    void *_dist;
931    //Pointer to the shortest path to the target node.
932    void *_path;
933    //Pointer to the distance of the target node.
934    int *_di;
935
936    public:
937    /// Constructor.
938
939    /// This constructor does not require parameters, therefore it initiates
940    /// all of the attributes to \c 0.
941    BfsWizardBase() : _g(0), _reached(0), _processed(0), _pred(0),
942                      _dist(0), _path(0), _di(0) {}
943
944    /// Constructor.
945
946    /// This constructor requires one parameter,
947    /// others are initiated to \c 0.
948    /// \param g The digraph the algorithm runs on.
949    BfsWizardBase(const GR &g) :
950      _g(reinterpret_cast<void*>(const_cast<GR*>(&g))),
951      _reached(0), _processed(0), _pred(0), _dist(0),  _path(0), _di(0) {}
952
953  };
954
955  /// Auxiliary class for the function-type interface of BFS algorithm.
956
957  /// This auxiliary class is created to implement the
958  /// \ref bfs() "function-type interface" of \ref Bfs algorithm.
959  /// It does not have own \ref run() method, it uses the functions
960  /// and features of the plain \ref Bfs.
961  ///
962  /// This class should only be used through the \ref bfs() function,
963  /// which makes it easier to use the algorithm.
964  template<class TR>
965  class BfsWizard : public TR
966  {
967    typedef TR Base;
968
969    ///The type of the digraph the algorithm runs on.
970    typedef typename TR::Digraph Digraph;
971
972    typedef typename Digraph::Node Node;
973    typedef typename Digraph::NodeIt NodeIt;
974    typedef typename Digraph::Arc Arc;
975    typedef typename Digraph::OutArcIt OutArcIt;
976
977    ///\brief The type of the map that stores the predecessor
978    ///arcs of the shortest paths.
979    typedef typename TR::PredMap PredMap;
980    ///\brief The type of the map that stores the distances of the nodes.
981    typedef typename TR::DistMap DistMap;
982    ///\brief The type of the map that indicates which nodes are reached.
983    typedef typename TR::ReachedMap ReachedMap;
984    ///\brief The type of the map that indicates which nodes are processed.
985    typedef typename TR::ProcessedMap ProcessedMap;
986    ///The type of the shortest paths
987    typedef typename TR::Path Path;
988
989  public:
990
991    /// Constructor.
992    BfsWizard() : TR() {}
993
994    /// Constructor that requires parameters.
995
996    /// Constructor that requires parameters.
997    /// These parameters will be the default values for the traits class.
998    /// \param g The digraph the algorithm runs on.
999    BfsWizard(const Digraph &g) :
1000      TR(g) {}
1001
1002    ///Copy constructor
1003    BfsWizard(const TR &b) : TR(b) {}
1004
1005    ~BfsWizard() {}
1006
1007    ///Runs BFS algorithm from the given source node.
1008
1009    ///This method runs BFS algorithm from node \c s
1010    ///in order to compute the shortest path to each node.
1011    void run(Node s)
1012    {
1013      Bfs<Digraph,TR> alg(*reinterpret_cast<const Digraph*>(Base::_g));
1014      if (Base::_pred)
1015        alg.predMap(*reinterpret_cast<PredMap*>(Base::_pred));
1016      if (Base::_dist)
1017        alg.distMap(*reinterpret_cast<DistMap*>(Base::_dist));
1018      if (Base::_reached)
1019        alg.reachedMap(*reinterpret_cast<ReachedMap*>(Base::_reached));
1020      if (Base::_processed)
1021        alg.processedMap(*reinterpret_cast<ProcessedMap*>(Base::_processed));
1022      if (s!=INVALID)
1023        alg.run(s);
1024      else
1025        alg.run();
1026    }
1027
1028    ///Finds the shortest path between \c s and \c t.
1029
1030    ///This method runs BFS algorithm from node \c s
1031    ///in order to compute the shortest path to node \c t
1032    ///(it stops searching when \c t is processed).
1033    ///
1034    ///\return \c true if \c t is reachable form \c s.
1035    bool run(Node s, Node t)
1036    {
1037      Bfs<Digraph,TR> alg(*reinterpret_cast<const Digraph*>(Base::_g));
1038      if (Base::_pred)
1039        alg.predMap(*reinterpret_cast<PredMap*>(Base::_pred));
1040      if (Base::_dist)
1041        alg.distMap(*reinterpret_cast<DistMap*>(Base::_dist));
1042      if (Base::_reached)
1043        alg.reachedMap(*reinterpret_cast<ReachedMap*>(Base::_reached));
1044      if (Base::_processed)
1045        alg.processedMap(*reinterpret_cast<ProcessedMap*>(Base::_processed));
1046      alg.run(s,t);
1047      if (Base::_path)
1048        *reinterpret_cast<Path*>(Base::_path) = alg.path(t);
1049      if (Base::_di)
1050        *Base::_di = alg.dist(t);
1051      return alg.reached(t);
1052    }
1053
1054    ///Runs BFS algorithm to visit all nodes in the digraph.
1055
1056    ///This method runs BFS algorithm in order to compute
1057    ///the shortest path to each node.
1058    void run()
1059    {
1060      run(INVALID);
1061    }
1062
1063    template<class T>
1064    struct SetPredMapBase : public Base {
1065      typedef T PredMap;
1066      static PredMap *createPredMap(const Digraph &) { return 0; };
1067      SetPredMapBase(const TR &b) : TR(b) {}
1068    };
1069    ///\brief \ref named-func-param "Named parameter"
1070    ///for setting PredMap object.
1071    ///
1072    ///\ref named-func-param "Named parameter"
1073    ///for setting PredMap object.
1074    template<class T>
1075    BfsWizard<SetPredMapBase<T> > predMap(const T &t)
1076    {
1077      Base::_pred=reinterpret_cast<void*>(const_cast<T*>(&t));
1078      return BfsWizard<SetPredMapBase<T> >(*this);
1079    }
1080
1081    template<class T>
1082    struct SetReachedMapBase : public Base {
1083      typedef T ReachedMap;
1084      static ReachedMap *createReachedMap(const Digraph &) { return 0; };
1085      SetReachedMapBase(const TR &b) : TR(b) {}
1086    };
1087    ///\brief \ref named-func-param "Named parameter"
1088    ///for setting ReachedMap object.
1089    ///
1090    /// \ref named-func-param "Named parameter"
1091    ///for setting ReachedMap object.
1092    template<class T>
1093    BfsWizard<SetReachedMapBase<T> > reachedMap(const T &t)
1094    {
1095      Base::_reached=reinterpret_cast<void*>(const_cast<T*>(&t));
1096      return BfsWizard<SetReachedMapBase<T> >(*this);
1097    }
1098
1099    template<class T>
1100    struct SetDistMapBase : public Base {
1101      typedef T DistMap;
1102      static DistMap *createDistMap(const Digraph &) { return 0; };
1103      SetDistMapBase(const TR &b) : TR(b) {}
1104    };
1105    ///\brief \ref named-func-param "Named parameter"
1106    ///for setting DistMap object.
1107    ///
1108    /// \ref named-func-param "Named parameter"
1109    ///for setting DistMap object.
1110    template<class T>
1111    BfsWizard<SetDistMapBase<T> > distMap(const T &t)
1112    {
1113      Base::_dist=reinterpret_cast<void*>(const_cast<T*>(&t));
1114      return BfsWizard<SetDistMapBase<T> >(*this);
1115    }
1116
1117    template<class T>
1118    struct SetProcessedMapBase : public Base {
1119      typedef T ProcessedMap;
1120      static ProcessedMap *createProcessedMap(const Digraph &) { return 0; };
1121      SetProcessedMapBase(const TR &b) : TR(b) {}
1122    };
1123    ///\brief \ref named-func-param "Named parameter"
1124    ///for setting ProcessedMap object.
1125    ///
1126    /// \ref named-func-param "Named parameter"
1127    ///for setting ProcessedMap object.
1128    template<class T>
1129    BfsWizard<SetProcessedMapBase<T> > processedMap(const T &t)
1130    {
1131      Base::_processed=reinterpret_cast<void*>(const_cast<T*>(&t));
1132      return BfsWizard<SetProcessedMapBase<T> >(*this);
1133    }
1134
1135    template<class T>
1136    struct SetPathBase : public Base {
1137      typedef T Path;
1138      SetPathBase(const TR &b) : TR(b) {}
1139    };
1140    ///\brief \ref named-func-param "Named parameter"
1141    ///for getting the shortest path to the target node.
1142    ///
1143    ///\ref named-func-param "Named parameter"
1144    ///for getting the shortest path to the target node.
1145    template<class T>
1146    BfsWizard<SetPathBase<T> > path(const T &t)
1147    {
1148      Base::_path=reinterpret_cast<void*>(const_cast<T*>(&t));
1149      return BfsWizard<SetPathBase<T> >(*this);
1150    }
1151
1152    ///\brief \ref named-func-param "Named parameter"
1153    ///for getting the distance of the target node.
1154    ///
1155    ///\ref named-func-param "Named parameter"
1156    ///for getting the distance of the target node.
1157    BfsWizard dist(const int &d)
1158    {
1159      Base::_di=const_cast<int*>(&d);
1160      return *this;
1161    }
1162
1163  };
1164
1165  ///Function-type interface for BFS algorithm.
1166
1167  /// \ingroup search
1168  ///Function-type interface for BFS algorithm.
1169  ///
1170  ///This function also has several \ref named-func-param "named parameters",
1171  ///they are declared as the members of class \ref BfsWizard.
1172  ///The following examples show how to use these parameters.
1173  ///\code
1174  ///  // Compute shortest path from node s to each node
1175  ///  bfs(g).predMap(preds).distMap(dists).run(s);
1176  ///
1177  ///  // Compute shortest path from s to t
1178  ///  bool reached = bfs(g).path(p).dist(d).run(s,t);
1179  ///\endcode
1180  ///\warning Don't forget to put the \ref BfsWizard::run() "run()"
1181  ///to the end of the parameter list.
1182  ///\sa BfsWizard
1183  ///\sa Bfs
1184  template<class GR>
1185  BfsWizard<BfsWizardBase<GR> >
1186  bfs(const GR &digraph)
1187  {
1188    return BfsWizard<BfsWizardBase<GR> >(digraph);
1189  }
1190
1191#ifdef DOXYGEN
1192  /// \brief Visitor class for BFS.
1193  ///
1194  /// This class defines the interface of the BfsVisit events, and
1195  /// it could be the base of a real visitor class.
1196  template <typename _Digraph>
1197  struct BfsVisitor {
1198    typedef _Digraph Digraph;
1199    typedef typename Digraph::Arc Arc;
1200    typedef typename Digraph::Node Node;
1201    /// \brief Called for the source node(s) of the BFS.
1202    ///
1203    /// This function is called for the source node(s) of the BFS.
1204    void start(const Node& node) {}
1205    /// \brief Called when a node is reached first time.
1206    ///
1207    /// This function is called when a node is reached first time.
1208    void reach(const Node& node) {}
1209    /// \brief Called when a node is processed.
1210    ///
1211    /// This function is called when a node is processed.
1212    void process(const Node& node) {}
1213    /// \brief Called when an arc reaches a new node.
1214    ///
1215    /// This function is called when the BFS finds an arc whose target node
1216    /// is not reached yet.
1217    void discover(const Arc& arc) {}
1218    /// \brief Called when an arc is examined but its target node is
1219    /// already discovered.
1220    ///
1221    /// This function is called when an arc is examined but its target node is
1222    /// already discovered.
1223    void examine(const Arc& arc) {}
1224  };
1225#else
1226  template <typename _Digraph>
1227  struct BfsVisitor {
1228    typedef _Digraph Digraph;
1229    typedef typename Digraph::Arc Arc;
1230    typedef typename Digraph::Node Node;
1231    void start(const Node&) {}
1232    void reach(const Node&) {}
1233    void process(const Node&) {}
1234    void discover(const Arc&) {}
1235    void examine(const Arc&) {}
1236
1237    template <typename _Visitor>
1238    struct Constraints {
1239      void constraints() {
1240        Arc arc;
1241        Node node;
1242        visitor.start(node);
1243        visitor.reach(node);
1244        visitor.process(node);
1245        visitor.discover(arc);
1246        visitor.examine(arc);
1247      }
1248      _Visitor& visitor;
1249    };
1250  };
1251#endif
1252
1253  /// \brief Default traits class of BfsVisit class.
1254  ///
1255  /// Default traits class of BfsVisit class.
1256  /// \tparam _Digraph The type of the digraph the algorithm runs on.
1257  template<class _Digraph>
1258  struct BfsVisitDefaultTraits {
1259
1260    /// \brief The type of the digraph the algorithm runs on.
1261    typedef _Digraph Digraph;
1262
1263    /// \brief The type of the map that indicates which nodes are reached.
1264    ///
1265    /// The type of the map that indicates which nodes are reached.
1266    /// It must meet the \ref concepts::ReadWriteMap "ReadWriteMap" concept.
1267    typedef typename Digraph::template NodeMap<bool> ReachedMap;
1268
1269    /// \brief Instantiates a ReachedMap.
1270    ///
1271    /// This function instantiates a ReachedMap.
1272    /// \param digraph is the digraph, to which
1273    /// we would like to define the ReachedMap.
1274    static ReachedMap *createReachedMap(const Digraph &digraph) {
1275      return new ReachedMap(digraph);
1276    }
1277
1278  };
1279
1280  /// \ingroup search
1281  ///
1282  /// \brief %BFS algorithm class with visitor interface.
1283  ///
1284  /// This class provides an efficient implementation of the %BFS algorithm
1285  /// with visitor interface.
1286  ///
1287  /// The %BfsVisit class provides an alternative interface to the Bfs
1288  /// class. It works with callback mechanism, the BfsVisit object calls
1289  /// the member functions of the \c Visitor class on every BFS event.
1290  ///
1291  /// This interface of the BFS algorithm should be used in special cases
1292  /// when extra actions have to be performed in connection with certain
1293  /// events of the BFS algorithm. Otherwise consider to use Bfs or bfs()
1294  /// instead.
1295  ///
1296  /// \tparam _Digraph The type of the digraph the algorithm runs on.
1297  /// The default value is
1298  /// \ref ListDigraph. The value of _Digraph is not used directly by
1299  /// \ref BfsVisit, it is only passed to \ref BfsVisitDefaultTraits.
1300  /// \tparam _Visitor The Visitor type that is used by the algorithm.
1301  /// \ref BfsVisitor "BfsVisitor<_Digraph>" is an empty visitor, which
1302  /// does not observe the BFS events. If you want to observe the BFS
1303  /// events, you should implement your own visitor class.
1304  /// \tparam _Traits Traits class to set various data types used by the
1305  /// algorithm. The default traits class is
1306  /// \ref BfsVisitDefaultTraits "BfsVisitDefaultTraits<_Digraph>".
1307  /// See \ref BfsVisitDefaultTraits for the documentation of
1308  /// a BFS visit traits class.
1309#ifdef DOXYGEN
1310  template <typename _Digraph, typename _Visitor, typename _Traits>
1311#else
1312  template <typename _Digraph = ListDigraph,
1313            typename _Visitor = BfsVisitor<_Digraph>,
1314            typename _Traits = BfsVisitDefaultTraits<_Digraph> >
1315#endif
1316  class BfsVisit {
1317  public:
1318
1319    ///The traits class.
1320    typedef _Traits Traits;
1321
1322    ///The type of the digraph the algorithm runs on.
1323    typedef typename Traits::Digraph Digraph;
1324
1325    ///The visitor type used by the algorithm.
1326    typedef _Visitor Visitor;
1327
1328    ///The type of the map that indicates which nodes are reached.
1329    typedef typename Traits::ReachedMap ReachedMap;
1330
1331  private:
1332
1333    typedef typename Digraph::Node Node;
1334    typedef typename Digraph::NodeIt NodeIt;
1335    typedef typename Digraph::Arc Arc;
1336    typedef typename Digraph::OutArcIt OutArcIt;
1337
1338    //Pointer to the underlying digraph.
1339    const Digraph *_digraph;
1340    //Pointer to the visitor object.
1341    Visitor *_visitor;
1342    //Pointer to the map of reached status of the nodes.
1343    ReachedMap *_reached;
1344    //Indicates if _reached is locally allocated (true) or not.
1345    bool local_reached;
1346
1347    std::vector<typename Digraph::Node> _list;
1348    int _list_front, _list_back;
1349
1350    //Creates the maps if necessary.
1351    void create_maps() {
1352      if(!_reached) {
1353        local_reached = true;
1354        _reached = Traits::createReachedMap(*_digraph);
1355      }
1356    }
1357
1358  protected:
1359
1360    BfsVisit() {}
1361
1362  public:
1363
1364    typedef BfsVisit Create;
1365
1366    /// \name Named template parameters
1367
1368    ///@{
1369    template <class T>
1370    struct SetReachedMapTraits : public Traits {
1371      typedef T ReachedMap;
1372      static ReachedMap *createReachedMap(const Digraph &digraph) {
1373        LEMON_ASSERT(false, "ReachedMap is not initialized");
1374        return 0; // ignore warnings
1375      }
1376    };
1377    /// \brief \ref named-templ-param "Named parameter" for setting
1378    /// ReachedMap type.
1379    ///
1380    /// \ref named-templ-param "Named parameter" for setting ReachedMap type.
1381    template <class T>
1382    struct SetReachedMap : public BfsVisit< Digraph, Visitor,
1383                                            SetReachedMapTraits<T> > {
1384      typedef BfsVisit< Digraph, Visitor, SetReachedMapTraits<T> > Create;
1385    };
1386    ///@}
1387
1388  public:
1389
1390    /// \brief Constructor.
1391    ///
1392    /// Constructor.
1393    ///
1394    /// \param digraph The digraph the algorithm runs on.
1395    /// \param visitor The visitor object of the algorithm.
1396    BfsVisit(const Digraph& digraph, Visitor& visitor)
1397      : _digraph(&digraph), _visitor(&visitor),
1398        _reached(0), local_reached(false) {}
1399
1400    /// \brief Destructor.
1401    ~BfsVisit() {
1402      if(local_reached) delete _reached;
1403    }
1404
1405    /// \brief Sets the map that indicates which nodes are reached.
1406    ///
1407    /// Sets the map that indicates which nodes are reached.
1408    /// If you don't use this function before calling \ref run(),
1409    /// it will allocate one. The destructor deallocates this
1410    /// automatically allocated map, of course.
1411    /// \return <tt> (*this) </tt>
1412    BfsVisit &reachedMap(ReachedMap &m) {
1413      if(local_reached) {
1414        delete _reached;
1415        local_reached = false;
1416      }
1417      _reached = &m;
1418      return *this;
1419    }
1420
1421  public:
1422
1423    /// \name Execution control
1424    /// The simplest way to execute the algorithm is to use
1425    /// one of the member functions called \ref lemon::BfsVisit::run()
1426    /// "run()".
1427    /// \n
1428    /// If you need more control on the execution, first you must call
1429    /// \ref lemon::BfsVisit::init() "init()", then you can add several
1430    /// source nodes with \ref lemon::BfsVisit::addSource() "addSource()".
1431    /// Finally \ref lemon::BfsVisit::start() "start()" will perform the
1432    /// actual path computation.
1433
1434    /// @{
1435
1436    /// \brief Initializes the internal data structures.
1437    ///
1438    /// Initializes the internal data structures.
1439    void init() {
1440      create_maps();
1441      _list.resize(countNodes(*_digraph));
1442      _list_front = _list_back = -1;
1443      for (NodeIt u(*_digraph) ; u != INVALID ; ++u) {
1444        _reached->set(u, false);
1445      }
1446    }
1447
1448    /// \brief Adds a new source node.
1449    ///
1450    /// Adds a new source node to the set of nodes to be processed.
1451    void addSource(Node s) {
1452      if(!(*_reached)[s]) {
1453          _reached->set(s,true);
1454          _visitor->start(s);
1455          _visitor->reach(s);
1456          _list[++_list_back] = s;
1457        }
1458    }
1459
1460    /// \brief Processes the next node.
1461    ///
1462    /// Processes the next node.
1463    ///
1464    /// \return The processed node.
1465    ///
1466    /// \pre The queue must not be empty.
1467    Node processNextNode() {
1468      Node n = _list[++_list_front];
1469      _visitor->process(n);
1470      Arc e;
1471      for (_digraph->firstOut(e, n); e != INVALID; _digraph->nextOut(e)) {
1472        Node m = _digraph->target(e);
1473        if (!(*_reached)[m]) {
1474          _visitor->discover(e);
1475          _visitor->reach(m);
1476          _reached->set(m, true);
1477          _list[++_list_back] = m;
1478        } else {
1479          _visitor->examine(e);
1480        }
1481      }
1482      return n;
1483    }
1484
1485    /// \brief Processes the next node.
1486    ///
1487    /// Processes the next node and checks if the given target node
1488    /// is reached. If the target node is reachable from the processed
1489    /// node, then the \c reach parameter will be set to \c true.
1490    ///
1491    /// \param target The target node.
1492    /// \retval reach Indicates if the target node is reached.
1493    /// It should be initially \c false.
1494    ///
1495    /// \return The processed node.
1496    ///
1497    /// \pre The queue must not be empty.
1498    Node processNextNode(Node target, bool& reach) {
1499      Node n = _list[++_list_front];
1500      _visitor->process(n);
1501      Arc e;
1502      for (_digraph->firstOut(e, n); e != INVALID; _digraph->nextOut(e)) {
1503        Node m = _digraph->target(e);
1504        if (!(*_reached)[m]) {
1505          _visitor->discover(e);
1506          _visitor->reach(m);
1507          _reached->set(m, true);
1508          _list[++_list_back] = m;
1509          reach = reach || (target == m);
1510        } else {
1511          _visitor->examine(e);
1512        }
1513      }
1514      return n;
1515    }
1516
1517    /// \brief Processes the next node.
1518    ///
1519    /// Processes the next node and checks if at least one of reached
1520    /// nodes has \c true value in the \c nm node map. If one node
1521    /// with \c true value is reachable from the processed node, then the
1522    /// \c rnode parameter will be set to the first of such nodes.
1523    ///
1524    /// \param nm A \c bool (or convertible) node map that indicates the
1525    /// possible targets.
1526    /// \retval rnode The reached target node.
1527    /// It should be initially \c INVALID.
1528    ///
1529    /// \return The processed node.
1530    ///
1531    /// \pre The queue must not be empty.
1532    template <typename NM>
1533    Node processNextNode(const NM& nm, Node& rnode) {
1534      Node n = _list[++_list_front];
1535      _visitor->process(n);
1536      Arc e;
1537      for (_digraph->firstOut(e, n); e != INVALID; _digraph->nextOut(e)) {
1538        Node m = _digraph->target(e);
1539        if (!(*_reached)[m]) {
1540          _visitor->discover(e);
1541          _visitor->reach(m);
1542          _reached->set(m, true);
1543          _list[++_list_back] = m;
1544          if (nm[m] && rnode == INVALID) rnode = m;
1545        } else {
1546          _visitor->examine(e);
1547        }
1548      }
1549      return n;
1550    }
1551
1552    /// \brief The next node to be processed.
1553    ///
1554    /// Returns the next node to be processed or \c INVALID if the queue
1555    /// is empty.
1556    Node nextNode() const {
1557      return _list_front != _list_back ? _list[_list_front + 1] : INVALID;
1558    }
1559
1560    /// \brief Returns \c false if there are nodes
1561    /// to be processed.
1562    ///
1563    /// Returns \c false if there are nodes
1564    /// to be processed in the queue.
1565    bool emptyQueue() const { return _list_front == _list_back; }
1566
1567    /// \brief Returns the number of the nodes to be processed.
1568    ///
1569    /// Returns the number of the nodes to be processed in the queue.
1570    int queueSize() const { return _list_back - _list_front; }
1571
1572    /// \brief Executes the algorithm.
1573    ///
1574    /// Executes the algorithm.
1575    ///
1576    /// This method runs the %BFS algorithm from the root node(s)
1577    /// in order to compute the shortest path to each node.
1578    ///
1579    /// The algorithm computes
1580    /// - the shortest path tree (forest),
1581    /// - the distance of each node from the root(s).
1582    ///
1583    /// \pre init() must be called and at least one root node should be added
1584    /// with addSource() before using this function.
1585    ///
1586    /// \note <tt>b.start()</tt> is just a shortcut of the following code.
1587    /// \code
1588    ///   while ( !b.emptyQueue() ) {
1589    ///     b.processNextNode();
1590    ///   }
1591    /// \endcode
1592    void start() {
1593      while ( !emptyQueue() ) processNextNode();
1594    }
1595
1596    /// \brief Executes the algorithm until the given target node is reached.
1597    ///
1598    /// Executes the algorithm until the given target node is reached.
1599    ///
1600    /// This method runs the %BFS algorithm from the root node(s)
1601    /// in order to compute the shortest path to \c t.
1602    ///
1603    /// The algorithm computes
1604    /// - the shortest path to \c t,
1605    /// - the distance of \c t from the root(s).
1606    ///
1607    /// \pre init() must be called and at least one root node should be
1608    /// added with addSource() before using this function.
1609    ///
1610    /// \note <tt>b.start(t)</tt> is just a shortcut of the following code.
1611    /// \code
1612    ///   bool reach = false;
1613    ///   while ( !b.emptyQueue() && !reach ) {
1614    ///     b.processNextNode(t, reach);
1615    ///   }
1616    /// \endcode
1617    void start(Node t) {
1618      bool reach = false;
1619      while ( !emptyQueue() && !reach ) processNextNode(t, reach);
1620    }
1621
1622    /// \brief Executes the algorithm until a condition is met.
1623    ///
1624    /// Executes the algorithm until a condition is met.
1625    ///
1626    /// This method runs the %BFS algorithm from the root node(s) in
1627    /// order to compute the shortest path to a node \c v with
1628    /// <tt>nm[v]</tt> true, if such a node can be found.
1629    ///
1630    /// \param nm must be a bool (or convertible) node map. The
1631    /// algorithm will stop when it reaches a node \c v with
1632    /// <tt>nm[v]</tt> true.
1633    ///
1634    /// \return The reached node \c v with <tt>nm[v]</tt> true or
1635    /// \c INVALID if no such node was found.
1636    ///
1637    /// \pre init() must be called and at least one root node should be
1638    /// added with addSource() before using this function.
1639    ///
1640    /// \note <tt>b.start(nm)</tt> is just a shortcut of the following code.
1641    /// \code
1642    ///   Node rnode = INVALID;
1643    ///   while ( !b.emptyQueue() && rnode == INVALID ) {
1644    ///     b.processNextNode(nm, rnode);
1645    ///   }
1646    ///   return rnode;
1647    /// \endcode
1648    template <typename NM>
1649    Node start(const NM &nm) {
1650      Node rnode = INVALID;
1651      while ( !emptyQueue() && rnode == INVALID ) {
1652        processNextNode(nm, rnode);
1653      }
1654      return rnode;
1655    }
1656
1657    /// \brief Runs the algorithm from the given source node.
1658    ///
1659    /// This method runs the %BFS algorithm from node \c s
1660    /// in order to compute the shortest path to each node.
1661    ///
1662    /// The algorithm computes
1663    /// - the shortest path tree,
1664    /// - the distance of each node from the root.
1665    ///
1666    /// \note <tt>b.run(s)</tt> is just a shortcut of the following code.
1667    ///\code
1668    ///   b.init();
1669    ///   b.addSource(s);
1670    ///   b.start();
1671    ///\endcode
1672    void run(Node s) {
1673      init();
1674      addSource(s);
1675      start();
1676    }
1677
1678    /// \brief Finds the shortest path between \c s and \c t.
1679    ///
1680    /// This method runs the %BFS algorithm from node \c s
1681    /// in order to compute the shortest path to node \c t
1682    /// (it stops searching when \c t is processed).
1683    ///
1684    /// \return \c true if \c t is reachable form \c s.
1685    ///
1686    /// \note Apart from the return value, <tt>b.run(s,t)</tt> is just a
1687    /// shortcut of the following code.
1688    ///\code
1689    ///   b.init();
1690    ///   b.addSource(s);
1691    ///   b.start(t);
1692    ///\endcode
1693    bool run(Node s,Node t) {
1694      init();
1695      addSource(s);
1696      start(t);
1697      return reached(t);
1698    }
1699
1700    /// \brief Runs the algorithm to visit all nodes in the digraph.
1701    ///
1702    /// This method runs the %BFS algorithm in order to
1703    /// compute the shortest path to each node.
1704    ///
1705    /// The algorithm computes
1706    /// - the shortest path tree (forest),
1707    /// - the distance of each node from the root(s).
1708    ///
1709    /// \note <tt>b.run(s)</tt> is just a shortcut of the following code.
1710    ///\code
1711    ///  b.init();
1712    ///  for (NodeIt n(gr); n != INVALID; ++n) {
1713    ///    if (!b.reached(n)) {
1714    ///      b.addSource(n);
1715    ///      b.start();
1716    ///    }
1717    ///  }
1718    ///\endcode
1719    void run() {
1720      init();
1721      for (NodeIt it(*_digraph); it != INVALID; ++it) {
1722        if (!reached(it)) {
1723          addSource(it);
1724          start();
1725        }
1726      }
1727    }
1728
1729    ///@}
1730
1731    /// \name Query Functions
1732    /// The result of the %BFS algorithm can be obtained using these
1733    /// functions.\n
1734    /// Either \ref lemon::BfsVisit::run() "run()" or
1735    /// \ref lemon::BfsVisit::start() "start()" must be called before
1736    /// using them.
1737    ///@{
1738
1739    /// \brief Checks if a node is reachable from the root(s).
1740    ///
1741    /// Returns \c true if \c v is reachable from the root(s).
1742    /// \pre Either \ref run() or \ref start()
1743    /// must be called before using this function.
1744    bool reached(Node v) { return (*_reached)[v]; }
1745
1746    ///@}
1747
1748  };
1749
1750} //END OF NAMESPACE LEMON
1751
1752#endif
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